Preparation of lubricating grease



United States Patent PREPARATION OF LUBRICATING GREASE Ira Edwin Puddington and Aurelio Frederick Sirianni,

()ttawa, Ontario, Canada, assignors to National Research Council, Ottawa, Ontario, Canada, a body corporate of Canada No Drawing. Application September 8, 1952,

Serial No. 308,526

Claims priority; application Canada September 2, 1952 14 Claims. (Cl. 25216) This invention relates to the preparation of lubricating grease from lubricating oil, which is generally but not necessarily a mineral lubricating oil.

It is well known that lubricating greases may be prepared by incorperating a solid, finely divided, low bulk density, absorbent material into a lubricating oil whereby the oil is retained in the interstitial spaces of the absorbent material and thickened. The most common absorbent material used has been silica gel, preferably in the form of the aerogel.

The difliculty has been found that normal absorbent materials of this type are hydrophilic and have a greater afiinity for water than for the oil. It has been found that, if greases prepared in the said manner come into contact with liquid water, or even water vapour, the water will be preferentially absorbed by the absorbent material and will displace the oil in such material. The grease will then distintegrate and lose its structural stability.

United States patent application Serial No. 275,016, made by the present inventors, discloses the production of a dried aerogel which has a water-repellent coating and may be added to a lubricating oil to form a lubricating grease. The process is to heat in an autoclave a moist mass of the aerogel and a solution of a coating substance in a solvent. On the vaporisation of the solvent in the autoclave, the aerogel is found to be coated with the coating substance. The coating substance may be a drying oil.

United States Patent No. 2,583,605, for which application was made by the present inventors, discloses a process for improving the structural stability of such greasesunderthe influence of water by using an inorganic gel as the absorbent material and waterproofing this gel with an alkyd resin which is optionally modified with a drying oil. This waterproofing may be effected before, during or after incorporating the gel into the oil.

It is the object of the present invention to provide a simplified process which possesses advantages over both the said prior inventions.

The process, according to, the present invention, comprises adding to a lubricating oil a drying oil and the requisite proportion of a solid, hydrophilic, finely divided, low bulk density, absorbent material, and polymerising the drying oil in situ. By the term requisite proportion is meant that proportion of the absorbent materialwhich is needed to produce a grease of the desired characteristics, e. g. 5-25 parts of such material by weight per 100 parts of the lubdicating oil. Methods of polymerising drying oil are well known in the art. It is possible to effect this polymerisation at room temperature, e. g. with the use of catalysts, but it is preferred to effect polymerisation by the application of heat. The heat treatment is suitably for 23 hours at 100150 C.

-It is found that the absorbent material adsorbs (i. e. on its surface) the drying oil which is then polymerised to form a substantially water-repellant coating. The invention essentially forms this coating in situ as, opposed to the invention covered in the said copending application serial No. 275,016 in which a coated, dried aerogel is prepared prior to incorporation in the lubricating oil. In comparison the present invention is a simplified process avoiding the isolation of a coated, dry gel and the use of an autoclave. Furthermore, the present invention is applicable to non-aerogels as well as aerogels, whereas the invention of the said copending application is restricted to the use of aerogels. f

The present invention is more economical than the invention disclosed in the said United States Patent No. 2,583,605 in the avoidance of the comparatively expensive alkyd resin which, moreover, needs more heat to be polymerised, e. g. of the order of 6 hours at 125 C. for a drying oil modified alkyd resin, than the heat treatment which is preferred to be used with the present invention to polymerise the drying oil.

In the preferred form of the invention, the proportion of drying oil used is limited so that substantially all of it is adsorbed by the absorbent material. This proportion is suitably 10100% by weight based on the absorbent material. Less than 100% could be used if only a small degree of water-repellancy were required.

Examples of suitable solid, hydrophilic, finely divided, low bulk density, adsorbent materials which may be used with the present invention are siliceous material (e. g.

silica aerogel and other silica gels), alumina, ferric oxide, cellulose and asbestos. Aquagels may be used but are not generally preferred since substantially all of the water must be evaporated by the heat treatment before a waterrepellant coating is formed and this is often difficult or inconvenient to effect. It is preferable to use aerogels or a gel containing a liquid miscible With the oil.

The mixture of lubricating oil, absorbent material and drying oil is preferably submitted to a shearing treatment, e. g. in a colloid mill, after polymerisation has been effected in order to break up highly agglomerated particles of the coated absorbent material.

The invention is illustrated by the examples below, in which any percentages given are by weight. In each example, the structural stability in the presence of water of the grease prepared is measured by the standard water test which involves placing the grease and some water in a long cylindrical container and continually raising and lowering a plunger therein over substantially the whole length of the cylindrical container. The plunger is apertured so that the grease and water are continually forced through it and thereby intimately mixed. The structural stability or water resistance of the grease is measured by the number of cycles (a cycle being a complete upward and downward movement of the plunger) of the plunger which the grease can stand without losing its structural stability, and this is the number given in the tables of the following examples. The tests were made to a maximum of 150 cycles so that greases tested to this point may well have stood further cycles. In the present case, the cylindrical container was 6" in length, l" in diameter and of 50 cc. capacity, and the plunger contained a single orifice in diameter. In each example, 5 grams of the grease was tested in the presence of 40 cc. of water at 70 C.

Example 1 Ten grams of boiled linseed oil was added to grams of 300 visc. V. I. mineral lubricating oil. Ten grams commercial silica aerogel was added to the solution and the system heated to C. for 2 hours. After passing through a colloid mill, this grease stood cycles of the said water test.

Example 2 The procedure of Example 1 was repeated only substituting the same quantity of tung oil for the linseed oil. The same results were obtained.

Example 3 The procedure of Example 2 was repeated only vary- Ten grams silica aerogel was added to 87 grams 300 visc. 95 V. 1. mineral lubrication oil containing 3 gm. tung oil. After heating for 2.5 hours at 125 C. and treating in a colloid mill, the system passed the water resistance test of 150 cycles.

Example 5 The procedure of Example 4 was repeated only using a heating temperature of 170 C. instead of 125 C.

After 45 minutes the system stood 18 cycles. After 80 minutes the system stood 150 cycles.

Example 6' The procedure of Example 4 was repeated only substituting the same quantity of dehydrated castor oil for the tung oil. After 1 hour at 125 C. the system stood 90 cycles.

Example 7 Per cent Acetone wetted, precipitated cellulose 9.0 Dehydrated castor oil 10.0 Mineral lubricating oil (300 visc. 40 V. I.) 81.0

This mixture was heated for 7 hours at 125 C. After passing through a colloid mill, the grease withstood at least 50 cycles.

Example 8 Per cent Fine asbestos 15 Dehydrated castor oil 15 Mineral lubricating oil (300 visc. 40 V. I.) 70

This mixture was heated for 4 hours at 125 C. After passing through a colloid mill, the grease withstood at least 50 cycles.

Example 9 The rate at which water rcpellency is imparted to silica aerogel drying oil systems is shown below.

A dispersion containing the following ingredients was prepared:

Per cent Silica aerogel 10 Tung oil 4 Mineral lubricating oil (300 visc. 95 V. I.) 86

This mixture was continuously stirred over a hot plate at 107 C., and then passed through a colloid mill. Aliquot samples (about 3-5 gm.) were taken at different intervals and, after treatment in a colloid mill, gave the following results under the water test:

2 /2 hours 150+ Example 10 A grease having the following composition was kept in a temperature controlled oven at 100 C.:

Per cent Silica aerogel l0 Tung oil 4 Mineral lubricating oil (300 visc. 95 V. I.) 86

The following results were obtained after various periods in the oven followed by treatment in a colloid mill:

Time: No. of cycles 1 hour 2-3 2.5 hours 4-5 5.5 hours 8-9 21 /2 hours 150+ Example 11 The grease prepared in accordance with Example 10, after treatment in a colloid mill, was kept at 51 C. for

These ingredients were heated with stirring at 125 C. The grease withstood 90 cycles of the plunger after 1 hour and over 150 cycles after 2 /2 hours, in each case after treatment in a colloid mill.

Example 13 Per cent Tung oil 3 Silica aerogel l0 Mineral lubricating oil (300 visc. V. I.) 87

The mixture was heated at 172 C. The grease withstood 18 cycles of the plunger after heating for 45 minutes and over 150 cycles after 80 minutes of heating, in each case after treatment in a colloid mill.

The above examples illustrate the use of mineral lubricating oil since this is the normal lubricating which will be used with the present invention. The invention is applicable, however, to other lubricating oils such as silicone oils, synthetic oils and vegetable lubricating oils.

We claim:

1. A process for the preparation of lubricating grease comprising adding to a mineral lubricating oil 5-25 parts by weight of a solid, hydrophilic, finely divided, low bulk density, absorbent material per parts of the lubricating oil and a drying oil in the proportion of 10-100% by weight of the absorbent material, and heating the mixture for 2-3 hours at 100-150 C.

2. A process as claimed in claim 1 in which the absorbent material is selected from the group consisting of silica aerogels and silica gels containing a liquid miscible with the lubricating oil.

3. A process for the preparation of lubricating grease comprising adding to a mineral lubricating oil' 5-25 parts by weight of a silica aerogel per 100 parts of the lubricating oil and a drying oil, selected from the group consisting of linseed oil, tung oil, and dehydrated castor oil and in the proportion of 10-100% by weight of the silica aerogel; heating the mixture for 2-3 hours at 100-150 C.; and then submitting the mixture to a shearing treatment.

4. A process for the preparation of lubricating grease comprising adding to a lubricating oil substantially 5-25 parts by weight of a solid, hydrophilic, finely divided, low bulk density, absorbent material per 100 parts of the lubricating oil and a drying oil in the proportion of substantially 10100% by weight of the absorbent material, and polymerising the drying oil in situ.

5. A process as claimed in claim 4 in which, after polymerisation, the mixture is submitted to a shearing treatment.

6. A process as claimed in claim 4 in which the drying oil is selected from the group consisting of linseed oil, tung oil and dehydrated castor oil.

7. A process as claimed in claim 4 in Which the absorbent material is selected from the group consisting of siliceous material, alumina, ferric oxide and asbestos.

8. A process as claimed in claim 4 in which the lubricating oil is a mineral lubricating oil.

9. A process as claimed in claim 4 in which the absorbent material is cellulose.

10. A process as claimed in claim 4 in which the heat treatment is for 2-3 hours at 100150 C.

11. A process for the preparation of lubricating grease comprising adding to a mineral lubricating oil substan tially 525 parts by weight of a solid, hydrophilic, finely divided, low bulk density, absorbent material per 100 parts of the lubricating oil and a drying oil in the proportion of substantially 10100% by Weight of the absorbent material, and heating the mixture to polymerise the drying oil.

12. A process for the preparation of lubricating grease comprising adding to a mineral lubricating oil an absorbent material, in the proportion of 525 parts by weight per 100 parts of the lubricating oil, and a drying oil, selected from the group consisting of linseed oil, tung oil and dehydrated castor oil and in the proportion of 10-100% by weight of the absorbent material; heating the mixture for 2-3 hours at 100-150 C.; and then submitting the mixture to a shearing treatment.

13. A process as claimed in claim 12 in which the absorbent material is selected from the group consisting of siliceous material, alumina, ferric oxide and asbestos, all in finely divided form.

14. A process as claimed in claim 12 in which the absorbent material is finely divided cellulose.

References Cited in the file of this patent UNITED STATES PATENTS 2,573,650 Peterson Oct. 30, 1951 2,583,605 Sirianni et al. Jan. 29, 1952 2,594,822 Stross et al Apr. 29, 1952 2,623,852 Peterson Dec. 30, 1952 

1. A PROCESS FOR THE PREPARATION OF LUBRICATING GREASE COMPRISING ADDING TO A MINERAL LUBRICATING OIL 5-25 PARTS BY EIGHT OF A SOLID, HYDROPHILIC, FINELY DIVIDED, LOW BULK DENSITY, ABSORBENT MATERIAL PER 100 PARTS OF THE LUBRICATING OIL AND A DRYING OIL IN THE PROPORTION OF 10-100% BY WEIGHT OF A SOLID, HYDROPHILIC, FINELY DIVIDED, LOW BULK FOR 2-3 HOURS AT 100-150* C. 